Head scratchinh situation

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

dusterdude

Full Access Member
Joined
Oct 7, 2020
Posts
355
Reaction score
379
Location
US
First Name
mark
Truck Year
1985
Truck Model
gmc c15
Engine Size
305
Ok guys,i recently installed a small cap electronic distributor with an external coil.it seems im not getting spark but,my timing light flashes when i crank the engine.im at a loss here and by the way,this is on a carbureted truck.does anyone have any ideas?
 

mxer147

83 K20, 350 vortec, 465, 208, 14/10, 4.10, 33s
Joined
Feb 8, 2023
Posts
607
Reaction score
2,191
Location
Colorado
First Name
Jack
Truck Year
1983
Truck Model
k20
Engine Size
350
when in doubt, I pull a plug wire off, put a small screwdriver into the plug socket, lay it across the exhaust manifold, and look for spark. No spark, I meter for 12 volt power at the coil, then to the next component until I find the failure point. If spark, make sure number one lines up with the rotor and the firing order is correct.
 

Redfish

Full Access Member
Joined
Nov 6, 2021
Posts
2,644
Reaction score
14,260
Location
Prairieville, LA
First Name
Andrew
Truck Year
1987
Truck Model
V1500
Engine Size
350/5.7
Ok guys,i recently installed a small cap electronic distributor with an external coil.it seems im not getting spark but,my timing light flashes when i crank the engine.im at a loss here and by the way,this is on a carbureted truck.does anyone have any ideas?

We can assume you stabbed the distributor correctly and that cylinder 1 is getting fire when it is supposed to? And that all the plug wires are re-oriented correctly?

It is possible that there is enough "spark" for your timing light to pick up but not enough spark to arc across the plugs and fire the engine.
 

dusterdude

Full Access Member
Joined
Oct 7, 2020
Posts
355
Reaction score
379
Location
US
First Name
mark
Truck Year
1985
Truck Model
gmc c15
Engine Size
305
Redfish,that is a damn good question.ill check it out
 

dusterdude

Full Access Member
Joined
Oct 7, 2020
Posts
355
Reaction score
379
Location
US
First Name
mark
Truck Year
1985
Truck Model
gmc c15
Engine Size
305
Back to this issue,i am getting 12.5 volts to the wire that plugs into the coil with key on but when i crank i only get about 10.5 volts on this wire.this seems to be recent phenomenon.does anyone where i should look for the drop?thanks
 

rusted nuts

Full Access Member
Joined
Mar 5, 2023
Posts
809
Reaction score
1,421
Location
Pa.
First Name
Jeffrey
Truck Year
1979
Truck Model
k20
Engine Size
4cly diesel
Back to this issue,i am getting 12.5 volts to the wire that plugs into the coil with key on but when i crank i only get about 10.5 volts on this wire.this seems to be recent phenomenon.does anyone where i should look for the drop?thanks
I would try running a ground wire from Dist hold down bolt to ext. coil 1st,, cheap n easy try
 

dusterdude

Full Access Member
Joined
Oct 7, 2020
Posts
355
Reaction score
379
Location
US
First Name
mark
Truck Year
1985
Truck Model
gmc c15
Engine Size
305
Would i ground the coil end to the hold down bolt on the coil too?
 

Snoots

Full Access Member
Joined
Jan 23, 2013
Posts
8,740
Reaction score
18,166
Location
Georgia
First Name
Roger
Truck Year
1973
Truck Model
Jimmy Sierra
Engine Size
350 w/203
It sounds like your wire from the battery to the starter is 'sinking' more than it should. Possibly due to age. 10.5 volts shouldn't cause an ignition problem tho while cranking.
 

Rickf

Full Access Member
Joined
Jul 29, 2017
Posts
571
Reaction score
713
Location
Grafton NH
First Name
Rick
Truck Year
1974, 1954 & a 1937
Truck Model
K20
Engine Size
350
You are having the same voltage drop issue that I have with my '74, however my truck started with a points distributor and the previous owner installed an HEI. To get mine to run I need it to get it spinning (key in start position) then let it go so it is in the run position. When I get around to it I'll eliminate the resistor wire, but for now this plus the extra pedal on the floor act as an anti-theft system.
What are the odds you have a resistor wire floating around?
How many small studs and/or wires are on your starter solenoid?
 

Turbo4whl

Supporting Member
Supporting Member
Joined
Oct 30, 2019
Posts
3,125
Reaction score
7,254
Location
Downingtown, PA
First Name
Wayne
Truck Year
1974
Truck Model
Jimmy
Engine Size
350
Back to this issue,i am getting 12.5 volts to the wire that plugs into the coil with key on but when i crank i only get about 10.5 volts on this wire.this seems to be recent phenomenon.does anyone where i should look for the drop?thanks
10.5 volts is all you will get at the coil when starter is cranking. The HEI will start with that voltage. What does your new distributor require? Should it have a capacitor wired in to maintain the voltage when cranking?

What is your new distributor, is it made to run with a processor?
 

dusterdude

Full Access Member
Joined
Oct 7, 2020
Posts
355
Reaction score
379
Location
US
First Name
mark
Truck Year
1985
Truck Model
gmc c15
Engine Size
305
Good questions on the distributor,ill have to get with the seller and ask.will advise when i get more info.thanks for the help.
 

hogdaddy

Full Access Member
Joined
Jan 12, 2023
Posts
127
Reaction score
237
Location
Alabama
First Name
mike
Truck Year
1986
Truck Model
Scottsdale
Engine Size
350
Which distributor and coil are you using? MSD, ACCEL?
 

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,444
Reaction score
8,676
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
First thing you need to verify you have spark,take out a plug attach the plug wire clamp the plug body in a jumper cable other end of jumper cable to ground,crank and look for spark. 2nd Make sure you're distributor was stabbed correctly.If the problem isn't solved by then you need to find out what distributor and coil you are running,they don't all wire the same and don't all trigger the same.
 

Forum statistics

Threads
44,156
Posts
950,545
Members
36,268
Latest member
JUKA
Top